1. Field of the Invention
The present invention relates to a rotary motor and a stator used for driving a medium used in a magnetic disk drive unit, optical disk drive unit or the like. More particularly, the present invention relates to the structure of the rotary motor and the stator in order to improve the mass productivity and to a method of manufacturing thereof.
2. Description of Related Art
A conventional rotary motor stator of this type (not shown) manufactured by stacking a plurality of ring-shaped board members blanking directly from a steel board, as disclosed in JP-A-100823/1982, for instance. However, yield of materials is low. For this reason, JP-B-46620/1985 discloses the improved yield by winding a belt-shaped board member with a large number of teeth in spiral while plastically deforming the board member to fasten a several layers by welding the respective layers.
As an another conventional method of manufacturing the rotary motor, there is a method disclosed in JP-A-98774/1999. FIGS. 48 and 49 are a view showing such a method.
Referring to FIGS. 48 and 49, the method involves feeding a strip-shaped magnetic material 500 to a press machine 502 through a work feeding machine 501, forming a core member 503 consists of thinned portions 503a, yoke members 503b, and magnetic pole teeth 503c, forming ring-shaped stacked yoke members 505 by winding a reel 504 by a plurality of turns such that the core member 503 corresponding to a plurality of stator cores are arranged during one turn, winding driving coils 506, dividing ring-shaped stacked yoke member 505 into blocks such that a stator core 507 corresponding to one rotary motor is provided, and producing stators for rotary motors by bending the stator core 507 with a tool.
The conventional rotary motor stators are constructed as above. Thus, the stator disclosed in JP-A-100823/1982 has not only the low yield of materials as mentioned above, but also is heavy to assemble thereof as the assembly forces a great number of the board members to be grasped one by one for conveyance. The stator disclosed in JP-B-46620/1985 has a difficulty in unfolding and dividing the stators for winding as the belt-shaped board member is wound up in spiral while plastically deforming. Regardless, they lack productivity.
Moreover, the method of manufacturing rotary motors disclosed in JP-A-98774/1999 has also the following problems.
(1) The diameter of connected stator cores 507 is very large compared with the thickness of stacked yoke member 505 for the reason that stator cores 507 corresponding to a plurality of rotary motors are connected in the circumferential direction. Therefore, the stacked yoke members 505 are apt to sag, which makes worse handling of stacked yoke members 505 in coating them with insulation coating and placing them onto the winding machine.
(2) It is difficult to provide a positioning portion for mounting the stator core 507 on the rotary motor and a stator-connecting for forming the stator core 507 in a ring and holding it for the reason that the yoke members having the same shape are continuously produced and they are wound up.
(3) The magnetic pole teeth 503c are stacked on the slant for the reason that the strip-shaped magnetic material 500 is provided with yoke members and the strip-shaped magnetic material 500 is wound up in a spiral form around a reel to form stacked yoke members 505. As a result, this incurs the deteriorated productivity in the winding process, and the decreased driving torque of the rotary motor and the torque ripple thereof.
The present invention has been made to solve the above problems. An object of the invention is to provide a stacked stator core capable of improving the workability in the winding process and the productivity of the product and a method of manufacturing the stator, and a rotary motor equipped with the stator and a method of manufacturing the rotary motor.